Life Twice Over: Earth's Origins May Trace To One Lifeless ForebearAnalysis of chemical reactions in single-celled organisms suggests that life on Earth may have emerged twice. Researchers propose that bacteria and archaea evolved independently from a common non-living precursor rather than descending from a single shared living cell. This hypothesis challenges the traditional theory of a Last Universal Common Ancestor (LUCA) for all existing life forms. Researchers examined internal cellular chemical reactions to trace the evolutionary trajectories of bacteria and archaea, the two largest groups of microorganisms. Interpretive Boundaries and LimitationsThe study does not provide a definitive answer regarding the exact mechanism of the origin of life.